p38 Mitogen-activated protein kinases is required for counteraction of 2-methoxyestradiol to estradiol-stimulated cell proliferation and induction of apoptosis in ovarian carcinoma cells via phosphorylation Bcl-2

Introduction: 2-Methoxyestradiol (2ME(2)), a natural endogenous product of estradiol (E-2) metabolism, has been shown to be a selective apoptotic agent for cancer cells but not for normal cells. In this study, we determined that 2ME(2) counteracts E-2-stimulated cell growth and induces apoptosis in ovarian carcinoma cells. In addition, we demonstrate that 2ME(2) induces apoptosis via p38 and phospho-Bcl2 pathway. Methods: 2ME(2) and/or E-2 were administered to the OVCAR-3 (human ovarian cancer) cell line. Cell growth inhibition was analyzed by [H-3] Thymidine incorporation assay and DNA fluorometric assay. Cell apoptosis was tested by DNA fragmentation analysis and FACS. The signaling pathway was determined by a series of biochemical assays. Results: 2ME(2) inhibited estradiol-stimulated cell growth and induced apoptosis in an ovarian carcinoma cell line. MAPK and p38, but not JNK, were found to be critical mediators in this process. Expression of a dominant negative mutant of p38 kinase or p38 specific inhibitor, SIB 203580, almost completely blocked the process. Furthermore, Bcl-2 phosphorylation was required for 2ME(2)-induced effects. Conclusion: Our data suggest that 2ME(2) inhibits E-2-stimulated proliferation and induces apoptosis in ovarian carcinoma cells. Furthermore, activation of p38 and phosphorylation of Bcl-2 plays a critical role in the mechanism. 2ME(2) therefore, may have a clinical application for the treatment of ovarian cancer.